I. Field of the Invention
This invention relates generally to apparatus for treating malignant tumors, and more particularly to metal seeds that may be implanted by injection into tumorous tissue for allowing simultaneous application of thermal energy and radioactive emissions to such tissue.
II. Discussion of the Prior Art
In a journal article entitled "Practical Aspects of Ferromagnetic Thermoseed Hyperthermia", published in the Radiologic Clinics of North America, Vol. 27, No. 3, dated May 1989, Ivan A. Brezovich and Ruby F. Meredith, both with the University of Alabama at Birmingham, presented a general treatise on a method of treating tumors by interstitially implanting small pieces of ferromagnetic alloy wire into the tissue and then exposing the subject to an externally applied, oscillating, magnetic field of a predetermined frequency and field strength so as to cause inductive heating of the thermoseeds within the body. This paper points out that by selected a ferromagnetic material having a proper Curie point, such thermoseeds becomes self-regulating when the temperature of the seed approaches the Curie point at which the material becomes non-magnetic. The Carter U.S. Pat. No. 5,133,710 relates to the same technology.
The Paulus et al. U.S. Pat. No. 5,429,583, which is assigned to the assignee of the present application, describes the use of a CoPd alloy as an improved material for such thermoseeds in that by properly adjusting the percent by weight of Co and Pd in the alloy, a Curie point temperature in a therapeutic range of temperatures (between 41.5.degree. C. and 100.degree. C.) and an increasing magnetization with temperature characteristic until the Curie point temperature is approached is achieved upon exposure to an oscillating magnetic field. That patent and the references cited therein are hereby incorporated by reference.
It is also known in the art that particles or seeds to be implanted in tumorous tissue can be coated or otherwise treated so as to emit radiation effective in irradiating and thereby killing the tumorous tissue without excessive damage to surrounding healthy tissue. In this regard, reference is made to the Kubiatowicz U.S. Pat. No. 4,323,055, the Russell, Jr. et al. U.S. Pat. Nos. 4,702,228 and 4,784,116 and the Suthanthiran U.S. Pat. No. 4,891,165 and the Carden Jr. U.S. Pat. No. 5,405,309, each of which describes techniques for making and utilizing radioactive seed implants.
For more than a decade, medical investigators have discussed the synergy of hyperthermia and radiation in the treatment of several types of tumors. The synergism is believed to be due to some form of combined damage on a cellular level, but increasingly, investigators are theorizing that the increase in blood flow during hyperthermia facilitates the radiation dose by lowering the percentage of hypoxic cells in the tumor. It has been widely known that poorly oxygenated tumors are much more resistant to radiation than normally oxygenated cell populations. Until now, no one has disclosed a combination implant that can produce both thermal and radioactive radiations simultaneously. Thus, producing an implant which is capable of delivering truly simultaneous heat and radiation is a unique advancement, as most clinical research in this area has used separate therapies spaced as close together as possible. The present invention provides just that type of desired implant.
The combination radioactive particle emission and thermal radiation seed implant of the present invention offers the further advantage in that once the radiation levels given off by the implants have virtually disappeared, the magnetic properties of the implants remain intact, allowing for continuous hyperthermia therapy fractions at any time in the future. In normal brachytherapy seeds, after the radiation has dissipated, the implants are completely inert and have no therapeutic value whatsoever.